High ISO performance (a6000)

Did some tests today comparing my a6000 to my RX100M3. I was kinda surprised. This was all done in raw, no high iso/long exposure reduction and imported in Photoshop CC without any adjustments.

When using the kitlens on the a6000, the chosen ISO values on the a6000 were WAY higher than what the RX100 chose. This is kinda logical since the RX100 has a faster lens than the a6000+kitlens. But I was surprised that even when setting the ISO values manually to ISO1600, ISO3200 and even ISO6400 the images from the RX100 tend to look nicer than what my a6000 is producing.

This story changes completely when using my a6000 with the Zeiss 24mm/1.8. I can't exactly say that iso performance is worse on the RX100 but the a6000 definitely retains more detail. So it seems that the a6000 only outperforms the RX100 when using a (very) fast lens.

Not judging, but I wonder if it's normal that the kitlens being less fast has such a negative impact on ISO performance. As it is now, and from what I'm seeing in the final pictures, the RX100M3 seems a more capable camera for indoor shots than the a6000 with the kitlens, kinda negating the usefulness of the kitlens indoors.